Full component utilization of lignocellulose : enzymatic hydrolysis after alkali-coupled binary DES pretreatment and valorization of the pretreatment liquor for sensing hydrogels

Abstract

The utilization of poplar wood as raw material to prepare high-value-added materials through green economic processes is of great significance for promoting the high-value utilization and sustainable development of biomass resources. In this study, pre-treatment of lignocellulose with a binary deep eutectic solvent (DES) of sodium hydroxide coupled with choline chloride and ethanolamine was conducted. The research shows that this pretreatment can efficiently remove lignin (with a maximum lignin removal rate of 68.12%), significantly enhance the enzymatic hydrolysis efficiency of cellulose and increase from less than 20% to over 90%. The pretreatment liquid is rich in lignin-derived active functional groups (such as hydroxyl and methoxy groups), which can form hydrogen bonds with acrylic acid monomers during hydrogel synthesis—this interaction serves as the core cross-linking mechanism to construct a stable hydrogel network, laying a solid foundation for the high-value utilization of pretreatment liquid. The hydrogel prepared from the pretreatment liquid at 120 °C exhibits the best mechanical properties with a tensile stress of up to 260 KPa. Moreover, the pretreatment liquid contains ions (such as Ch⁺ and Cl⁻), endowing it with inherent ionic conductivity of up to 0.53 S/m without the need for additional conductive media. The application of the hydrogel prepared from the 120 °C pretreatment liquid in the field of flexible sensors, especially for human motion signals (such as joint bending) is a very promising direction for the high-value utilization of lignocellulosic biomass resources.